• Corrosion Science and Technology
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• v.18 no.6
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• pp.221-227
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• 2019

During the operation, maintenance and decommissioning of nuclear power plant radioactive contaminated waste is produced. This waste is stored in an underground repository 60-100 meters below the surface. The metallic portion of this waste comprises mostly carbon and stainless steel. A long-term field exposure showed high corrosion rates, general corrosion up to 29 ㎛ a^-1 and localized corrosion even higher. High corrosion rate is possible if microbes produce corrosive products, or alter the local microenvironment to favor corrosion. The bacterial and archaeal composition of biofilm formed on the surface of carbon steel was studied using 16S rRNA gene targeting sequencing, followed by phylogenetic analyses of the microbial community. The functional potential of the microbial communities in biofilm was studied by functional gene targeting quantitative PCR. The corrosion rate was calculated from weight loss measurements and the deposits on the surfaces were analyzed with SEM/EDS and XRD. Our results demonstrate that microbial diversity on the surface of carbon steel and their functionality is vast. Our results suggest that in these nutrient poor conditions the role of methanogenic archaea in corrosive biofilm, in addition to sulphate reducing bacteria, could be greater than previously suspected.

• Journal of Environmental Science International
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• v.14 no.9
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• pp.861-871
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• 2005

This study was carried out to get more operational characteristics of Anoxic(anaerobic)-Oxic-Anoxic-Oxic $(AO)_2$ sequencing batch biofilm reactors (SBBRs) at the low TOC concentration, The operating time in anoxic (anaerobic) time to oxic time was I : I. Experiments were conducted to find the effects of the aeration time distribution on the organic matters and nutrients removal. Three lab-scale reactors were fed with synthetic wastewater based on glucose as carbon source. During studies, the operation mode was fixed. The first aeration time to the second aeration time in SBBR-I was 2 : 3, and those in SBBR-2 and SBBR-3 were I : 4 and 3 : 2, respectively. The organic removal efficiency didn't show large difference among three reactors of different aeration time distribution. However, from these study results, the optimum aeration time distribution in the first and the second aeration time for biological nutrient removal was shown as 3 : 2. The release of phosphorus was inhibited at the second non-aeration period because of the low TOC concentration and the nitrate produced by the nitrification at the first aeration period.

• IE interfaces
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• v.11 no.3
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• pp.23-40
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• 1998

In this paper, a method to determine the optimal configuration of operating policies in an integrated-automated manufacturing system using the Taguchi method and computer simulation experiments is presented. An integrated-automated manufacturing system called direct-input-output manufacturing system(DIOMS) is described. We only consider the operational aspect of the DIOMS. Four operating policies including input sequencing control, dispatching rule for the storage/retrieval(S/R) machine, machine center-based part type selection rule, and storage assignment policy are treated as design factors. The number of machine centers, the number of part types, demand rate, processing time and the rate of each part type, vertical and horizontal speed of the S/R machine, and the size of a local buffer in the machine centers are considered as noise factors in generating various manufacturing system environment. For the performance characteristics, mean flow time and throughput are adopted. A robust design experiment with inner and outer orthogonal arrays are conducted by computer simulation, and an optimal configuration of operating policies is presented which consists of a combination of the level of each design factor. The validity of the optimal configurations is investigated by comparing their signal-to-noise ratios with those obtained with full factorial designs.

• Journal of Microbiology and Biotechnology
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• v.20 no.1
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• pp.179-186
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• 2010

In biological wastewater treatment, high lipid concentrations can inhibit the activity of microorganisms critical to the treatment process and cause undesirable biomass flotation. To reduce the inhibitory effects of high lipid concentrations, a two-phase anaerobic system, consisting of an anaerobic sequencing batch reactor (ASBR) and an upflow anaerobic sludge blanket (UASB) reactor in series, was applied to synthetic dairy wastewater treatment. During 153 days of operation, the two-phase system showed stable performance in lipid degradation. In the ASBR, a 13% lipid removal efficiency and 10% double-bond removal efficiency were maintained. In the UASB, the chemical oxygen demand (COD), lipid, and volatile fatty acid (VFA) removal efficiencies were greater than 80%, 70%, and 95%, respectively, up to an organic loading rate of 6.5 g COD/l/day. No serious operational problems, such as significant scum formation or sludge washout, were observed. Protein degradation was found to occur prior to degradation during acidogenesis.

• Environmental Engineering Research
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• v.20 no.4
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• pp.370-376
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• 2015

This study investigated the effects of various arsenite concentrations on bio-hydrogen production from molasses using a sequence batch reactor (SBR) operated in a series of three batch cycles. In the first batch cycle, hydrogen production was stimulated at arsenite concentrations lower than 2.0 mg/L, while inhibition occurred at arsenite concentration higher than 2.0 mg/L compared to the control. Hydrogen production decreased substantially during the second batch cycle, while no hydrogen was produced during the third batch cycle at all tested concentrations. The toxic density increased with respect to the increase in arsenite concentrations (6.0 > 1.6 > 1.0 > 0.5 mg/L) and operation cycles (third cycle > second cycle > first cycle). The presence of microorganisms such as Clostridium sp. MSTE9, Uncultured Dysgonomonas sp. clone MEC-4, Pseudomonas parafulva FS04, and Uncultured bacterium clone 584CL3e9 resulted in active stimulation of hydrogen production, however, it was unlikely that Enterobacter sp. sed221 was not related to hydrogen production. The tolerance of arsenite in hydrogen producing microorganisms decreased with the increase in induction time, which resulted in severing the inhibition of continuous hydrogen production.

• Journal of Korean Society on Water Environment
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• v.33 no.1
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• pp.90-96
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• 2017

Many sewage treatment plants have applied the advanced technology of chemical coagulant system to remove phosporus in Korea. However there are some problems for the injection of optimum coagulant dosage. In order to solve these problems, the research related to the more cost-effective automatic total phosphorus coagulation control system using an EC(Electrical Conductivity) have been in progress. This study was conducted by the same process and operation method as the Lab-scale for public small town sewage treatment plant. First, it confirmed the correlation among the EC, PO4-P and coagulant dosage in the Lab-scale MSBR(Membrane Sequencing Batch Reactor) process. Next, it analyzed that correlation coefficient of EC and the coagulant dosage was 0.92 in the Full-scale MSBR process. As a result, not only T-P removal efficiency was doubled but also it satisfied the effluent water quality standard in a stable manner. In addition, by applying the automatic control system using the EC, compared to the fixed coagulant injection system the coagulant dosage could be reduced by 28%.

• Journal of Korean Society on Water Environment
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• v.30 no.2
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• pp.220-225
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• 2014

A sequencing batch reactor (SBR) was operated to obtain thiosulfate-utilizing denitrifier cultivated with two types of electron accepter (nitrate and nitrite). Using the microbial biomass obtained from the SBR, batch tests were conducted with different nitrite concentrations (50 and 100 mg-N/L) at pH 7.0, 7.5 and 7.9 to see how free nitrous acid (FNA) negatively works on the thiosulfate-utilizing denitrification of nitrate. The specific denitrification rate (SDR) of nitrate was significantly influenced by pH and FNA. The presence of nitrite caused a remarked decrease of the SDR under low pH conditions, because of the microbiological inhibitory effect of FNA. The minimum SDR was observed when initial nitrite concentration was 100 mg-N/L at pH 7.0. Moreover. the SDR was influenced by the type of electron acceptor used during the SBR operation. Thiosulfate-utilizing denitrifier cultivated with nitrite showed smaller SDR on the thiosulfate-utilizing denitrification of nitrate than those cultivated with nitrate.

• Journal of Environmental Science International
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• v.16 no.7
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• pp.813-821
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• 2007

Laboratory scale experiments were conducted to investigate the removal characteristics of nitrogen and phosphorus in two sequencing batch biofilm reactors (SBBRs). SBBR1 had a short first non-aeration period and SBBR2 had a long first non-aeration period. The removal characteristics of nitrogen and phosphorus in each SBBR were precisely observed according to the variation of influent TOC concentration, and the operation control parameters (pH, DO concentration, ORP) in each reactor were measured. In biological nitrogen removal, there was little difference between SBBR1 and SBBR2 and the nitrogen removal efficiencies were very low. The nitrogen and phosphorus removal characteristics in high influent TOC concentration were different from those in low TOC. Nitrogen removals by simultaneous nitrification/denitrification (SND) were occurred in both SBBR1 and SBBR2. The P removal in SBBR1 was superior to that in SBBR2. The second P release was observed in SBBR1 which had long second non-aeration period.

• Journal of Korean Society of Water and Wastewater
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• v.38 no.1
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• pp.29-38
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• 2024

Wastewater management is increasingly emphasizing economic and environmental sustainability. Traditional methods in sewage treatment plants have significant implications for the environment and the economy due to power and chemical consumption, and sludge generation. To address these challenges, a study was conducted to develop the Intermittent Cycle Extended Aeration System (ICEAS). This approach was implemented as the primary technique in a full-scale wastewater treatment facility, utilizing key operational factors within the standard Sequencing Batch Reactor (SBR) process. The optimal operational approach, identified in this study, was put into practice at the research facility from January 2020 to December 2022. By implementing management strategies within the biological reactor, it was shown that maintaining and reducing chemical quantities, sludge generation, power consumption, and related costs could yield economic benefits. Moreover, adapting operations to influent characteristics and seasonal conditions allowed for efficient blower operation, reducing unnecessary electricity consumption and ensuring proper dissolved oxygen levels. Despite annual increases in influent flow rate and concentration, this study demonstrated the ability to maintain and reduce sludge production, electricity consumption, and chemical usage. Additionally, systematic responses to emergencies and abnormal situations significantly contributed to economic, technical, and environmental benefits.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.2
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• pp.79-86
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• 2016

The purpose of this study is to efficiently improve biological sequencing batch reactor (SBR) system of high-concentrated nitrate nitrogen in reverse osmosis (RO) concentrates by total dissolved solids (TDS) regulation. Since a laboratory-scale SBR system had been operated, we had analyzed specific denitrification rate (SDNR) and specific oxygen uptake rate (SOUR) for microbial activity in according to various injection concentration of TDS. As a result, higher injection concentration of TDS decreased SDNR, and delayed denitrification within denitrification process. Moreover, the higher injection concentration of TDS was, the lower microbial activity was during operation of laboratory-scale SBR system. Therefore, the regulation of TDS injection concentration is necessary to improve efficiency of nitrate nitrogen in the biological SBR system, and treatment of calcium ion ($Ca^{2+}$) is also specifically focused to remove nitrate nitrogen. Moreover, analytical data of SDNR and SOUR can be the effective kinetic design parameters to application of biological treatment of RO concentrate by aerobic granular sludge (AGS).